致谢：感谢一路支持我完成论文的人

As my thesis is about to be completed, I'd like to express my gratitude to those who have supported and encouraged me to reach this point. I am thankful for their encouragement and companionship throughout my university life. Firstly, I'd like to thank my supervisor, Professor Xie Gaofu. For the past four years, Professor Xie has given me meticulous guidance and support, which has greatly benefited me. Not only have I accumulated professional knowledge, but I have also become aware of the errors and shortcomings that I should avoid in my future academic research. Finally, I want to thank my parents and friends for their companionship and support during my studies.